Steward Observatory/NSF’s NOIRLab Joint Colloquium Series: The Long Term Time Variability and Triggering of Supermassive Black Hole Growth

Abstract: It is now well established that the most intense supermassive black hole (SMBH) growth episodes (luminous Active Galactic Nuclei, or AGN) are variable at all time scales, ranging from minutes/hours to billions of years. This has significant implications for our understanding of the cosmic history of SMBH growth and its connection to galaxy evolution. In this talk, I will start by presenting our study of an interesting galaxy population showing large-scale signatures of a powerful AGN, while the small scale signatures point to a much weaker nuclear source in the recent past. These objects suggest the presence of an AGN that has faded 1-2 dex over a timescale of 10^{4-5} yrs, far beyond what can be observed in a human lifetime. I will present our detailed studies of these sources using spatially-resolved IFU spectroscopy with VLT/MUSE, and discuss how these sources fit in our general understanding of the time dependence of the SMBH growth over 13 orders of magnitude in time.

At longer time-scales, I will discuss the observational and theoretical evidence for a link between major galaxy mergers and the most rapid SMBH growth episodes.  In this scenario, the more traditional AGN unification paradigm in which orientation is the main parameter only holds at lower luminosities. At the same time, for the more violent accretion events, originated by major mergers, we find evidence for an evolutionary sequence in which the AGN is first heavily obscured (Compton-thick) to reveal an unobscured quasar later.  I will give estimates of how much SMBH growth activity we are currently missing due to this heavy obscuration, and why it is critical to reach a complete census of the SMBH mass density in the Universe and its evolution.

Finally, I will present results from our multi-wavelength studies of a sample of nearby confirmed dual AGN (pairs of growing SMBHs with nuclear separation <10 kpc). Specifically, I will focus on our ongoing program to obtain optical and near-IR IFU spectroscopy and ALMA maps for several dual AGN at z<0.1, with nuclear separations ranging from ~5 kpc to ~200pc. These high-resolution multi-wavelength studies allow us to understand the complex connection between black hole growth and galaxy evolution in this critical stage.

 *Graduate students will meet with Dr. Treister for lunch on Thursday at 12:00 PM (AZ) in room N305.